1. Field of the Invention
This invention relates to a machine translation apparatus, a machine translation method and a computer program product for optimum translation based on a semantic relation between words.
2. Description of the Related Art
Conventionally, the range of application of machine translation has been limited to technical documents or the like having limited sentence patterns. With the recent development of the machine translation technique, however, a wide range of documents including Web documents have come to be capable of being handled for machine translation. Also, the combination of the machine translation technique and the speech recognition technique has given rise to a situation in which the practical application of a spoken language translation (SLT) apparatus (interpretation machine) for translating the human speech in the real world in real time.
The spoken language translation is required to accommodate the language phenomena different from a written language, such as the word ellipses, omissions of functional words, word order inversions, filled pauses, or filler insertions, and thus has many problems yet to be overcome for practical application.
One of these problems is the frequent use of a deixis in the spoken language. The deixis is defined as an expression including a deictic word such as “this” or “that” and a pronoun such as “I” or “you,” directly reffering to an object in the utterance environment. When a deixis is used, the translation without identifying a referent could not lead to an appropriate translation and deteriorate the translation quality.
The English sentence “Can I take this?” including the deixis “this,” for example, can be translated into Japanese sentence without identifying the referent. In this case, however, the verb “take” will be translated into the Japanese verb “toru,” meaning “get into one's hands,” while “take” has a lot of other appropriate translations according to a context. To guarantee a more accurate translation, what is referred by “this,” which is a direct object of “take,” is required to be resolved. When “this” could be resoloved to refer a taxi, for example, the translation of “take” will be “noru” that means “travel or go by means of a certain kind of transportation,” or when the “this” could be resolved to refer a bath, the appropriate translation will be “hairu,” meaning “get into somewhere.”
By identifying the referent of the deixis in this way, a more appropriate translation is made possible and the translation quality can be improved. A conventional technique of anaphora resolution has been proposed to resolve a referent of a deixis by searching a proper antecedent from the preceding speech, but the accuracy is not enough to practical use.
On the other hand, U.S. Pat. No. 6,868,383 discloses a technique in which the input speech including a deixis is properly interpreted by identifying the referent of the deixis, whose referent is displayed on a screen of a PDA (personal digital assistance). When a user makes an utterance with deixis, he or she is required to point a object on the screen by a mouse or pen, simultaneously. This technique makes it possible to identify the referent of a deixis even in the absence of a preceding speech.
The technique disclosed in U.S. Pat. No. 6,868,383, however, presupposes the presence of a referent in a virtual space of the screen on PDA. This technique, therefore, poses the problem of a very limited application range, when applied to spoken language translation, since SLT will be used in a various environment and the referred object can be anything in the real world.